Resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage.
Level 3 - non-randomized controlled study
Prospective longitudinal repeated-measures interventional study without a control group.
PubMed 27219125 · doi:10.1113/JP272472
What was done
Ten young men (mean age 27 ± 1 years) completed a 10-week resistance training program. Muscle biopsies of the vastus lateralis were taken before, 24 h, and 48 h post-resistance exercise at week 1 (T1), week 3 (T2), and week 10 (T3). Integrated myofibrillar protein synthesis (MyoPS) was measured using deuterium oxide, muscle damage was assessed by Z-band streaming and indirect parameters, and muscle fiber cross-sectional area (fCSA) was evaluated at T1, T2, and T3 to measure hypertrophy.
What was found
Increases in fCSA were statistically significant only at T3 (P = 0.017). Changes in MyoPS post-exercise were greater at T1 (P < 0.03) than at T2 and T3, with similar values between T2 and T3. Muscle damage was highest during post-exercise recovery at T1, attenuated at T2, and minimal at T3. Post-exercise MyoPS was not correlated with hypertrophy at T1, but post-exercise MyoPS at both T2 and T3 strongly correlated with hypertrophy (r ≈ 0.9, P < 0.04).
Why it matters
Early increases in muscle protein synthesis in untrained individuals reflect repair of muscle damage rather than growth. Protein synthesis rates only correlate with muscle hypertrophy after the initial damage response is attenuated by regular training.
Limits
The sample size is small (n = 10) and limited to young men. The study lacked a non-exercising control group, and the abstract omits absolute quantitative values and confidence intervals for fCSA, MyoPS, and muscle damage markers.
Cited by
- contradicts When you exercise a muscle, you tear the muscle fibers, which build back stronger to increase muscle mass.